JP6514212B2 - Conductive carbon powder, method for producing the same and use thereof - Google Patents

Description

  The present invention relates to a conductive carbon powder essentially consisting of lignin, a process for its preparation and its use. The powder originates from the conductive carbon intermediate product and may also originate essentially from lignin. Further disclosed is its use and a composition comprising said carbon powder. In addition, a method of producing said conductive carbon powder is also disclosed together with a method of making said composition, which also comprises a conductive carbon intermediate which essentially results from lignin.

  Electrically conductive plastics are used in many different applications where electromagnetic interference and electrostatic discharge have to be avoided. Examples include packaging materials for household appliances, casings for computers or mobile phones, pipes and tanks for flammable liquids such as gasoline tanks, electric wires and cables, and the like. Conventional plastics (thermoplastics and thermosetting plastics) have low conductivity and they tend to create static electricity. They can be given dissipative or even conductivity by adding the ground conductive material at a level above the so-called percolation threshold. The resulting compound, which comprises plastic and conductive material, is referred to as conductive plastic. However, the mechanical performance of the plastic is impaired as the addition of the ground conductive material reduces the impact strength and the ductility. High performance conductive materials reach the penetration threshold at low addition levels and maintain the mechanical performance of the plastic. The most commonly used conductive materials are conductive carbon blacks, i.e. special and expensive grades of carbon black.

Carbon black is produced by pyrolyzing oil with fuel gas in a furnace. In the formation of conductive carbon black, pyrolysis is followed by expensive post-treatment steps to increase the conductivity, in particular, steam exposure to increase the surface area and extraction to remove contaminants. Carbon blacks, particularly conductive carbon blacks, have a strong negative impact on the environment, and fossil raw materials are used in high-energy mass production processes and therefore emit high amounts of CO ₂ .
Thus, there is a need for new, competitive, high performance conductive materials for the production of conductive plastics.

In addition, low environmental impact, and the conductive material emissions with little CO ₂ is also required.
During the chemical pulping process, cellulose fibers are separated from softwood (softwood), hardwood (hardwood), and annual biomass from biomass and are further processed into paper, cardboard, tissue paper products or chemicals. The separation is carried out in liquid, for example in the so-called white liquor in the kraft pulping process or in organic solvents such as in the organosolv process. Lignin can be isolated from the spent liquor and then used as a biofuel or as a feedstock for chemicals and materials.

According to a first aspect, the present invention provides one or more of the above problems by providing a conductive carbon powder which essentially originates from lignin (i.e. originates from lignin), preferably essentially from lignin. Solve
According to a second aspect, the present invention also provides a conductive carbon intermediate product essentially derived from lignin having the form of a powder or shaped body, such as a wafer, bar, rod, film, filament or fleece etc. .

The present invention also provides, according to a third aspect, a method of producing a conductive carbon powder according to the first and second aspects comprising the following steps:
a) heat treating the lignin-containing compound to increase the carbon content to at least 80% to obtain the conductive carbonized lignin intermediate product, and b) the conductive carbonized lignin to obtain the conductive carbonized lignin powder Mechanical processing of intermediate products.
The present invention also provides, according to a fourth aspect, a method of producing a conductive carbon powder according to the first and second aspects, comprising the following steps:
i) supplying lignin and at least one additive;
ii) mixing the components;
iii) forming the mixture to form a formed body;
iv) heat treating the shaped body in at least one stage where the last stage comprises a temperature gradient from room temperature to about 2000 ° C. under an inert atmosphere, thus providing the conductive carbonized intermediate product ;
v) grinding the conductive carbonized intermediate product and thus providing conductive carbon powder.

According to a fifth aspect, the present invention also provides a method of producing a carbonized intermediate product in filament form comprising the following steps:
vi) supplying lignin and at least one additive;
vii) mixing the components and melt spinning the mixture into monofilament or multifilament bundle components;
viii) heat treatment of the shaped body in two steps including a temperature gradient from room temperature to about 2000 ° C. in a final step under an inert atmosphere, thus the conductive carbonized intermediate product in filament form Supply stage.
The present invention also provides a conductive carbon powder obtainable by the method of the third or fourth aspect according to the sixth aspect.
The invention also provides, according to a seventh aspect, a conductive carbonized intermediate product in the form of a filament obtainable by the method of the fifth aspect.
According to an eighth aspect, the present invention is an additive for producing a conductive polymer composition, which is used in applications such as computer and mobile phone casings, automobile devices, electric wires, cables, pipes and aircraft devices. There is also provided use of the conductive carbon powder according to the first, second or fifth aspect of the present invention.

The present invention also relates to the use of the conductive carbon powder according to the first, second or fifth aspect as an additive for producing a conductive polymer composition for protection against electromagnetic interference or electrostatic discharge according to the ninth aspect provide.
The invention also provides according to a tenth aspect a composition comprising a conductive carbon powder and a polymer according to the first, second or fifth aspect, preferably a thermoplastic polymer or a thermosetting polymer or a mixture of such polymers. .
The invention also provides a method of producing a composition according to the tenth aspect, comprising mixing the conductive carbon powder with a polymer, preferably a thermoplastic polymer or a thermosetting polymer or a mixture of such polymers according to the eleventh aspect. provide.

The invention also provides, according to a twelfth aspect, a polymer composition obtainable by the method according to the eleventh aspect.
The present invention relates to the polymer composition according to the tenth or twelfth aspect according to the thirteenth aspect, in a conductive material such as a computer, a mobile phone, a device of a car, a wire, a cable, a pipe and a material used for a device of an aircraft. It also provides the use of
According to a fourteenth aspect, the invention provides a polymer for the semiconductive layer of a cable comprising an electrically conductive carbon powder according to the first, second or fifth aspect and a thermoplastic or thermosetting polymer or a mixture of such polymers. Also provided is a composition.

The expression "lignin" is intended throughout the specification to include lignin which can be used to make conductive carbon powder. Examples of said lignin include, but are not limited to, lignin obtained via various fractionation methods such as softwood lignin, hardwood lignin, lignin from annual plants or organosolv lignin or kraft lignin. Lignin can be obtained, for example, by using the method disclosed in European patent application EP 1794363.
The expression "conductive carbon powder" is intended throughout the present specification to comprise powdery substances which consist of 80% or more of carbon, for example having the ability to impart conductivity to thermoplastics or thermosetting substances. . Furthermore, the thermoplastic or thermosetting material can be a polymer of fossil origin. Furthermore, the powder can be a substitute for carbon black obtained from fossil sources.

  The expression "additive" is intended throughout the specification to include, for example, additives which facilitate the production of lignin-containing compositions in melt extrusion or melt spinning for further processing to conductive carbonized lignin powder. Examples include, but are not limited to, reactive agents that impart melt extrudability to lignin such as plasticizers (eg PEG, eg PEG 400 as an example), aliphatic acids or lignin solvents. The lignin solvent is an aprotic polar solvent such as aliphatic amides such as dimethylformamide (DMF) or dimethylacetamide (DMAc), tertiary amine oxides such as N-methylmorpholine-N-oxide (NMMO), dimethylsulfoxide DMSO), ethylene glycol, di-ethylene glycol, low molecular weight polyethylene glycol (PEG) having a molecular weight between 150 and 20,000 g / mole, or an ionic liquid or any combination of said solvents and liquids.

  The expression "thermoplastic" includes thermoplastic polymers (which may be of fossil origin), which may be useful in the context of using conductive carbon powder (which is also the context in which carbon black is used) Is intended throughout the present specification. Said polymers are, without limitation, acrylates such as PMMA, PP (polypropylene), PE (polyethylene) such as HDPE (high density PE), MDPE (medium density PE), LDPE (low density PE), PA (polyamide) such as It can be nylon, PS (polystyrene), polyvinyl chloride (PVC), polysulfone, ether ketone or polytetrafluoroethylene (PTFE). Furthermore, PE may be crosslinked (PEX). Furthermore, it may be a copolymer comprising two or more of said polymers or a mixture comprising two or more of said polymers.

The expression "thermosetting" includes thermosetting polymers (which may be of fossil origin), which may be useful in the context of using conductive carbon powders, which use carbon black It is intended throughout the present specification that the situation is included. The polymer can be, without limitation, polyurethane, polyester, phenol-formaldehyde, urea-formaldehyde, melamine, epoxy, cyanate ester, vulcanized rubber and polyimide. Furthermore, it may be a copolymer comprising two or more of said polymers or a mixture comprising two or more of said polymers.
According to a preferred embodiment of the fourth aspect of the present invention the additive is polyethylene glycol.
According to a preferred embodiment of the fourth aspect of the present invention the temperature gradient from room temperature is up to 1600 ° C.

According to a preferred embodiment of the fourth aspect of the present invention the temperature gradient from room temperature is up to 1400 ° C.
According to a preferred embodiment of the tenth aspect of the present invention, the polymer is a thermoplastic polymer or a thermosetting polymer, or a mixture of such polymers, used for the preparation of the conductive compound.
According to a preferred embodiment of the tenth aspect of the invention, the polymer is a polymeric olefin, a copolymer comprising a polyolefin or a mixture of polyolefins.
According to a preferred embodiment of the tenth aspect of the present invention the polymer is polypropylene (PP).

According to a preferred embodiment of the tenth aspect of the present invention, the conductive carbon powder, when formulated, further enhances the penetration threshold of the polymer compound at an addition level of 1 to 40%. The blending includes mixing (blending) the polymer and the carbon powder in a molten state.
According to a preferred embodiment of the tenth aspect of the present invention, the conductive carbon powder, when formulated, reduces the volume resistivity of the polymer compound after the permeation point to 10 < ⁰ > to 10 < ⁶ > ohm-cm.
According to a preferred embodiment of the fourteenth aspect of the present invention the thermoplastic polymer is a polyolefin, a copolymer comprising a polyolefin or a mixture of polyolefins.
According to a fifteenth aspect of the present invention, the temperature range of the second heat treatment step may be from room temperature to 1600 ° C., or to 1200 ° C., or to 1000 ° C. In the first heat treatment stage, the temperature can be up to 300.degree.

  Preferred features of each aspect of the invention are as for each of the other aspects mutatis mutandis. The prior art document (s) described herein are incorporated to the fullest extent permitted by law. The invention will be further described in the following examples, together with the accompanying drawings, which in no way limit the scope of the invention. The embodiments of the present invention will be described and explained in more detail using the example of embodiment together with the attached drawings, the sole purpose of which is to explain the present invention and the intention to limit its scope is entirely Absent.

FIG. 1 discloses the volume resistivity of a compound composed of PP (HP561R from Lyondell Basell) and 5% and 10% of the conductive carbon powder described in the present invention, respectively. Comparative penetration curves are shown for reference compositions containing PP and three different commercially available conductive carbon blacks, respectively. A comparison of volume resistivity of compressed carbon powder is disclosed (the applied pressure is 31 MPa). A comparison of the volume resistivity of carbonized fibers is disclosed.

Examples of lignin-containing compounds in the form of shaped bodies
Example 1
The laboratory twin-screw with a single capillary from a mixture consisting of 88% by weight softwood kraft lignin, 7% by weight phthalic anhydride and 5% by weight DMSO (purity 97%, Sigma-Aldrich) Melt spinning was performed using an extruder (DSM Xplore Micro Compounder). The lignin-containing compound obtained was in the form of a filament 150 μm in diameter.

Example 2
The mixture from Example 1 was extruded using a laboratory twin screw extruder (KEDSE 20/40 "from Brabender GmbH & CO. KG) using a multifilament die equipped with 62 capillaries. The lignin-containing compound was in the form of a bundle of multifilaments having a single filament diameter of 72 μm.

Example 3
A mixture was prepared containing 90% by weight softwood lignin and 10% PEG 400 (polyethylene glycol from Sigma-Aldrich, molecular weight 400 Da).
The mixture was extruded using a die equipped with 62 capillaries for a laboratory twin screw extruder. The resulting lignin-containing compound was in the form of a bundle of multifilaments having a single filament diameter of 90 μm.

Example 4
The mixture was prepared as described in Example 3 and placed in a flat metal tube. Pressure was applied using a piston so that the lignin containing compound was in the form of a wafer.
Examples for conductive carbon intermediate products

Example 5
The lignin-containing filaments from Example 1 were converted in a two-step heat treatment to obtain the conductive carbon intermediate product. In the first stage, the filaments are heated in air from room temperature to 250 ° C., at a heating rate varying between 0.2 ° C./min and 5 ° C./min, and then in the second stage at room temperature in nitrogen. To 1600 ° C. at a heating rate of 1 ° C./min. The resulting conductive carbon intermediate product was in the form of a filament having a diameter of about 60 μm and had an electrical volume resistivity of 1.4 × 10 ⁻³ Ω · cm. Volume resistivity was measured using an LCR meter.

Example 6
The spun filaments obtained from Example 2 were heat treated in the same manner as described in Example 5. The resulting carbonized multifilament had a diameter of about 80 μm and an electrical volume resistivity of 0.5 × 10 ⁻³ Ω · cm.

Example 7
The filaments obtained from Example 3 were heat treated in the same manner as described in Example 5. The resulting carbonized multifilament had a diameter of about 75 μm and an electrical volume resistivity of 0.6 × 10 ⁻³ Ω · cm.

Example 8
The filaments obtained from Example 3 were heat treated according to the following steps. In the first stage, the filaments are heated in air from room temperature to 250 ° C., at a heating rate varying between 0.2 ° C./min and 5 ° C./min, and then in the second stage at room temperature in nitrogen. To 1000 ° C. at a heating rate of 2 ° C./min. The carbonized fiber obtained had an electrical volume resistivity of 0.72 × 10 ⁻³ Ω · cm.

Example 9
The filaments obtained from Example 3 were heat treated according to the following steps. In the first stage, the filaments are heated in air from room temperature to 250 ° C., at a heating rate varying between 0.2 ° C./min and 5 ° C./min, and then in the second stage at room temperature in nitrogen. To 1200 ° C. at a heating rate of 2 ° C./min. The carbonized fiber obtained had an electrical volume resistivity of 0.33 × 10 ⁻³ Ω · cm.

Example 10
The filaments obtained from Example 3 were heat treated according to the following steps. In the first stage, the filaments are heated in air from room temperature to 250 ° C., at a heating rate varying between 0.2 ° C./min and 5 ° C./min, and then in the second stage at room temperature in nitrogen. To 1400 ° C. at a heating rate of 2 ° C./min. The carbonized fiber obtained had an electrical volume resistivity of 0.23 × 10 ⁻³ Ω · cm.

Example 11
The filaments obtained from Example 3 were heat treated according to the following steps. In the first stage, the filaments are heated in air from room temperature to 250 ° C., at a heating rate varying between 0.2 ° C./min and 5 ° C./min, and then in the second stage at room temperature in nitrogen. To 1600 ° C. at a heating rate of 2 ° C./min. The carbonized fiber obtained had an electrical volume resistivity of 0.54 × 10 ⁻³ Ω · cm.

Example 12
The wafer from Example 4 was heat treated in a nitrogen atmosphere by raising the temperature from room temperature to 1600 ° C. at a heating rate of 1 ° C./min to obtain a carbonized wafer.

Example of conductive carbon powder
Example 13
The carbonized wafer from Example 12 was milled manually using a laboratory mortar to obtain a conductive carbonized lignin powder.

Examples of conductive polymer compounds
Example 14
The conductive carbonized lignin powder from Example 14 was formulated into a polypropylene matrix (HP561R from Lyondell Basell) using a DSM Xplore micro-compounder. The MFR was 25 g / 10 min (230 ° C./2.16 kg / 10 min). The composition consisted of 95% by weight of polypropylene and 5% of conductive carbonized lignin powder. The extruded strand has a volume resistivity of 5.2 × 10 ⁵ Ω · cm, which is described in the literature (Debowska, M. et al .: Positron annihilation in carbon black-polymer composites, Radiation Physics and Chemistry 58 (2000), The volume resistivity of pure PP reported in H.5-6, S.575-579) was considerably lower than about 1 × 10 ¹⁷ Ω · cm. From this example, it was found that the conductive carbonized lignin powder from Example 13 was actually conductive.

Example 15
The conductive carbon powder from Example 14 was formulated into a polypropylene matrix (HP561R from Lyondell Basell) using a DSM Xplore micro-compounder. The composition consisted of 90% by weight of (PP) and 10% of conductive carbonized lignin powder. The extruded strand had a volume resistivity of 2.6 × 10 ⁵ Ω · cm.

Example of Reference Conductive Polymer Compound
Example 16
Fig. 1 shows literature data on volume resistivity of conductive polymer compositions containing different commercially available conductive carbon blacks (Debowska, M. et al .: Positron annihilation in carbon black-polymer composites, Radiation Physics and Chemistry 58 (2000), H. 5 to 6, S. 575 to 579). Commercially available carbon blacks were SAPAC-6 (from CarboChem), Printex XE-2 (from Degussa) and Vulcan XC-72 (Cabot).
Figure 1 additionally discloses the volume resistivity of a composition comprising the PP described above (HP 561R from Lyondell Basell) and 5% and 10% conductive carbon powder, respectively.
From the figure, it can be seen that the conductive carbonized lignin powder provided by the present invention has at least the same conductive performance as the best commercially available carbon black (Printex XE-2).

Example 17
The powder was loaded into a hollow cylinder to determine the conductivity of the powder sample. This cylinder was made of non-conductive PMMA and was thoroughly cleaned between each measurement. The internal diameter was 5 mm. At the bottom of the cylinder was a gold-plated copper plate as a base electrode. The second electrode was a copper stamp, also gold plated to form a second electrode. The stamp was then inserted into the cylinder and the powder was slowly compressed. The applied pressure and the volume in the powder-filled chamber were plotted via force measurement and online position measurement. A DC voltage could be applied to the two electrodes to measure absolute resistance. With the recorded position of the stamp, the volume resistivity could be calculated.
The resistivity values could only be compared at equal pressure levels to compare for different samples having specific volumes that may vary. In the results shown, the chamber was filled with powder and compressed to a maximum pressure of 31 MPa. The measured values are shown in FIG.
From the results shown in the figure, it is clear that lignin-based carbonized powder (CLP) exhibits the same conductivity / resistivity performance as commercial grade of Cabot (Cabot Vulcan XC-72-R).
In the figure,
Example 13-1 = Example 13 above
Example 13-2 = Example 13 but with manual grinding with a laboratory mortar, but with cryomilling.

Example 18
The products in Examples 8-11 above were also compared to commercial grade carbon fiber (Toho Tenax HTA 406k and Mitsubishi Dialead K13C, respectively, their values were obtained from the product sheet and the Internet, respectively). The results are shown in FIG.
While various embodiments of the present invention have been described above, one of ordinary skill in the art will appreciate further minor variations that fall within the scope of the present invention. The breadth and scope of the present invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. For example, any of the above compositions or methods can be combined with other known methods. Other aspects, advantages and modifications within the scope of the invention will be apparent to those skilled in the art to which the invention pertains.

Claims (5)

A method of producing conductive carbon powder which results essentially from lignin comprising the following steps:
To obtain a) conductive carbonized lignin intermediate product, heat treating lignin-containing compounds which increase at least 80% carbon content, and b) to obtain a carbonized lignin powder having conductivity, the conductive carbide lignin Grinding the intermediate product. A method of producing conductive carbon powder which results essentially from lignin comprising the following steps:
i) supplying lignin and at least one additive,
ii) mixing the components;
iii) molding the mixture to form a molded body,
iv) a heat treatment of the shaped body in at least one stage comprising a temperature gradient of from room last stage under an inert atmosphere to 2 000 ° C., supplying the thus conductive carbonized intermediate product ,
v) grinding the conductive carbonized intermediate product and thus providing conductive carbon powder. The method according to claim 2 , wherein the additive is polyethylene glycol. 3. The method of claim 2 , wherein the temperature gradient from room temperature is up to 1600 < 0 > C. The method according to claim 2 , wherein the temperature gradient from room temperature is up to 1 400 ° C.